Low latency physical downlink control channel and physical downlink shared channel
Methods, systems, and devices for wireless communication are described. A base station may indicate time and frequency resources for a low latency physical downlink control channel (sPDCCH), which may be different from another physical downlink control channel (PDCCH), to a user equipment (UE). The base station may then transmit a common sPDCCH (CsPDCCH) message to indicate which low latency control channel elements (sCCEs) are used for sPDCCH transmission during a given subframe. In some cases, the signaling used to indicate the initial resource allocation for sPDCCH may be infrequent relative to the CsPDCCH transmissions. If some of the resources initially allocated for sPDCCH are not actually used for sPDCCH during a subframe, the base station and the UE may use those resources for communicating data. For example, the base station may transmit data using a low latency physical downlink shared channel (sPDSCH) to the UE using those resources.
1. A method for wireless communication in a system that supports communication using a first duration transmission time interval (TTI) and a second duration TTI that is shorter than the first duration TTI, comprising:
receiving signaling that identifies resources for a control channel associated with the second duration TTI;
receiving a user-specific control message of the control channel within the first duration TTI based at least in part on the signaling, wherein a location of the control channel within the first duration TTI is based at least in part on a location of a data region of the second duration TTI, wherein the first duration TTI and the second duration TTI at least partially overlap in time; and
communicating data using a portion of the resources for the control channel based at least in part on a location of the user-specific control message and a grant received in the user-specific control message.
2. The method of claim 1 , further comprising:
receiving a control message of the control channel for indicating to at least one user equipment (UE) a subset of the resources for the control channel used for transmitting the control channel; and
identifying the portion of the resources for the control channel that are used for communicating data based at least in part on the control message.
3. The method of claim 2 , wherein the control message comprises a bitmap corresponding to the subset of the resources for the control channel, wherein each bit of the bitmap indicates whether one or more control channel elements (CCEs) of the identified resources for the control channel are used for transmitting the control channel.
4. The method of claim 2 , further comprising:
performing a rate matching operation for the data based at least in part on the control message, wherein the data is communicated based at least in part on the rate matching operation.
5. The method of claim 1 , further comprising:
identifying a search space for the control channel based at least in part on the identified resources; and
performing a blind decoding operation based at least in part on the search space, wherein the user-specific control message is received based at least in part on the blind decoding operation.
6. The method of claim 1 , wherein the signaling comprises an indication of one or more symbol periods used for the control channel, an indication of frequency domain resources used for the control channel, or an aggregation level of a control message, or any combination thereof.
7. The method of claim 1 , wherein the resources for the control channel comprise a pattern of control channel elements (CCEs) associated with two symbol duration TTIs, slot duration TTIs, or both.
8. The method of claim 7 , wherein the first duration TTI comprises a subframe duration TTI, the second duration TTI comprises a two symbol duration TTI, and wherein the resources for the control channel include resources located after a first symbol and a second symbol of a slot duration TTI.
9. The method of claim 7 , wherein each CCE of the pattern corresponds to a first symbol of a two symbol duration TTI.
10. The method of claim 7 , wherein one or more CCEs of the pattern include a plurality of symbol periods associated with a slot duration TTI duration.
11. The method of claim 7 , wherein the CCEs associated with slot duration TTIs and the CCEs associated with two symbol duration TTIs each comprise two symbol periods.
12. The method of claim 7 , wherein the CCEs associated with slot duration TTIs comprise two symbol periods and the CCEs associated with two symbol duration TTIs comprise one symbol period.
13. The method of claim 1 , further comprising:
determining whether a TTI is a two symbol duration TTI or a slot duration TTI based at least in part on the signaling or the user-specific control message.
14. The method of claim 1 , further comprising:
receiving one or more cell-specific reference signals (CRS) or demodulation reference signals (DMRS) based at least in part on the resources for the control channel.
15. The method of claim 1 , further comprising:
identifying a resource block group (RBG) size, wherein the data is communicated based at least in part on the RBG size.
16. A method for wireless communication in a system that supports communication using a first duration transmission time interval (TTI) and a second duration TTI that is shorter than the first duration TTI, comprising:
transmitting signaling that identifies resources for a control channel associated with the second duration TTI;
transmitting a user-specific control message of the control channel within the first duration TTI based at least in part on the signaling, wherein a location of the control channel within the first duration TTI is based at least in part on a location of a data region of the second duration TTI, wherein the first duration TTI and the second duration TTI at least partially overlap in time; and
communicating data using a portion of the resources for the control channel identified in the user-specific control message.
17. The method of claim 16 , further comprising:
identifying the portion of the resources for the control channel that are used for transmitting the control channel; and
transmitting a control message of the control channel for indicating to at least one user equipment (UE) a subset of the resources used for transmitting the control channel.
18. The method of claim 17 , wherein the control message comprises a bitmap corresponding to the subset of the resources for the control channel, wherein each bit of the bitmap indicates whether one or more control channel elements (CCEs) of the identified resources for the control channel are used for transmitting the control channel.
19. The method of claim 16 , further comprising:
performing a rate matching operation for the data based at least in part on the portion of the resources for the control channel that are used for transmitting the control channel.
20. The method of claim 16 , wherein the resources for the control channel comprise a pattern of control channel elements (CCEs) associated with two symbol duration TTIs, slot duration TTIs, or both.
21. An apparatus for wireless communication in a system that supports communication using a first duration transmission time interval (TTI) and a second duration TTI that is shorter than the first duration TTI, comprising:
a processor;
memory in electronic communication with the processor; and
instructions stored in the memory, wherein the instructions are executable by the processor to:
receive signaling that identifies resources for a control channel associated with the second duration TTI;
receive a user-specific control message of the control channel within the first duration TTI based at least in part on the signaling, wherein a location of the control channel within the first duration TTI is based at least in part on a location of a data region of the second duration TTI, wherein the first duration TTI and the second duration TTI at least partially overlap in time; and
communicate data using a portion of the resources for the control channel based at least in part on a location of the user-specific control message and a grant received in the user-specific control message.
22. The apparatus of claim 21 , further comprising instructions executable by the processor to:
receive a control message of the control channel for indicating to at least one user equipment (UE) a subset of the resources for the control channel used for transmitting the control channel; and
identify the portion of the resources for the control channel that are used for communicating data based at least in part on the control message.
23. The apparatus of claim 22 , wherein the control message comprises a bitmap corresponding to the subset of the resources for the control channel, wherein each bit of the bitmap indicates whether one or more control channel elements (CCEs) of the identified resources for the control channel are used for transmitting the control channel.
24. The apparatus of claim 22 , further comprising instructions executable by the processor to:
perform a rate matching operation for the data based at least in part on the control message, wherein the data is communicated based at least in part on the rate matching operation.
25. The apparatus of claim 21 , further comprising instructions executable by the processor to:
identify a search space for the control channel based at least in part on the identified resources; and
perform a blind decoding operation based at least in part on the search space, wherein the user-specific control message is received based at least in part on the blind decoding operation.
26. An apparatus for wireless communication in a system that supports communication using a first duration transmission time interval (TTI) and a second duration TTI that is shorter than the first duration TTI, comprising:
a processor;
memory in electronic communication with the processor; and
instructions stored in the memory, wherein the instructions are executable by the processor to:
transmit signaling that identifies resources for a control channel associated with the second duration TTI;
transmit a user-specific control message of the control channel within the first duration TTI based at least in part on the signaling, wherein a location of the control channel within the first duration TTI is based at least in part on a location of a data region of the second duration TTI, wherein the first duration TTI and the second duration TTI at least partially overlap in time; and
communicate data using a portion of the resources for the control channel identified in the user-specific control message.
27. The apparatus of claim 26 , further comprising instructions executable by the processor to:
identify the portion of the resources for the control channel that are used for transmitting the control channel; and
transmit a control message of the control channel for indicating to at least one user equipment (UE) a subset of the resources used for transmitting the control channel.
28. The apparatus of claim 27 , wherein the control message comprises a bitmap corresponding to the subset of the resources for the control channel, wherein each bit of the bitmap indicates whether one or more control channel elements (CCEs) of the identified resources for the control channel are used for transmitting the control channel.
29. The apparatus of claim 26 , further comprising instructions executable by the processor to:
perform a rate matching operation for the data based at least in part on the portion of the resources for the control channel that are used for transmitting the control channel.
30. The apparatus of claim 26 , wherein the resources for the control channel comprise a pattern of control channel elements (CCEs) associated with two symbol duration TTIs, slot duration TTIs, or both.